Angioplasty procedures are well known within the medical community. During such a procedure, a catheter is navigated through a lumen of the human body to a site needing expansion. For example, a distal portion of a catheter containing a deflated balloon is directed to an area of an artery which is substantially blocked, and which can be enlarged upon expansion of the balloon.
All currently known balloon catheters are pneumatically actuated. More specifically, the balloon catheter is manufactured from an elastomeric conduit with an enlarged diameter portion thereof forming a balloon. Upon the balloon reaching the procedure site, pressurized fluid is directed through the conduit and to the balloon so as to enlarge the diameter of the balloon, thereby imparting force against the interior walls of the lumen and thus expanding the blocked area. In order to minimize the entrance diameter of the puncture hole through the skin into the arterial system and thereby decrease the time for healing, as well as the amount of scar tissue after healing, it is of major importance to be able to reduce the diameter of the balloon catheter system while non-pressurized.
Currently such angioplasty catheters are being made using either compliant or non-compliant elastomeric material. Due to the necessity of being able to use high forces to open up blocked arteries, fluid pressures used to actuate the balloon can be very high (more than 20 atmosphere). With a compliant balloon material, this requires very thick elastomeric materials to be used. Thick compliant materials can withstand such high pressures, and adequately retract into their original dimension to allow for retraction through the lumen, however their thickness is counter to the desire of having non-expanded small dimensions. Non-compliant balloon materials can be constructed having thinner balloon wall dimensions, but a downside of using non-compliant balloon materials is that they have to be folded to reduce their non-expanded size.
Moreover, both compliant as well as non-compliant balloon materials have to be pneumatically actuated, therefore one has to provide a fluid access lumen through the complete catheter system. The walls of such an access lumen have to be sufficiently strong to withstand the pressure, but this design demand is in contrast to using highly flexible, thin catheter systems.
A further downside of using a pneumatic actuation principle for expanding the balloons is the risk of having leaks in the balloon. These can originate during expansion in calcified lesions. As the creation of leaks will prevent further expansion, this can lead to very serious situations, for example, with a balloon expanded stent procedure, this can lead to a partially-deployed, and thus unstable, stent. As a result, the catheter is often of a thick and bulky shaft-like construction. For most applications, small diameters and high flexibility are of great importance. For example, with neurological procedures, or procedures within the lower extremities having mostly torturous vessels, such fluid-driven elastomeric catheters and their relatively large diameters, are simply unusable. Further complicating matters is the fact that such balloon constructions can only be made to a certain minimum diameter, thus preventing usage in such lumens, as well as lumens which have been reduced to a small diameter due to a condition requiring the angioplasty. Especially challenging is the use of current balloon catheters when stenting a bifurcation. This requires two balloons to be used in parallel, doubling the space requirements.